Dialga is the first one that comes to mind as it's a pretty potent Trick Room setter, can beat Fairies and has an immunity to sandstorm damage; other than that, Druddigon makes for a decent abuser thanks to it's slowness (48 base speed iirc, I didn't check) and access to neat things like Sheer Force, Sucker Punch and Gunk Shot. Most other Dragons are pretty fast or else don't have a lot of utility under Trick Room, but if I think of anything else I'll edit it in here. For future reference, though, this might be a more pertinent question to ask in the dedicated
Dragon Cup thread - we normally have a thread that goes up whenever these competitions are announced :]